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Inappropriate activation of the tumour-suppressor protein p53 during development can promote phenotypes similar to those of CHARGE syndrome, suggesting that p53 activation not only has a beneficial function in suppressing cancer but also a deleterious function in promoting developmental syndromes. CHARGE syndrome promoted by activated p53 The complex congenital disorder known as CHARGE syndrome results in many phenotypes, including heart defects, retarded growth and development, genital hypoplasia and ear abnormalities. Most CHARGE syndrome patients have mutations in the gene for the chromatin remodeller protein CHD7, but in mouse the Chd7 mutation is embryonically lethal, and not all CHARGE syndrome phenotypes are evident. Laura Attardi and colleagues now demonstrate that inappropriate activation of the p53 tumour suppressor gene during development can promote CHARGE phenotypes in mice, including ocular coloboma and defects of both the outer and inner ear, which are typical of CHARGE syndrome and rare in other conditions. The findings that p53 mutations can drive both cancer and developmental diseases throws a new light on the function of p53 in vivo . CHARGE syndrome is a multiple anomaly disorder in which patients present with a variety of phenotypes, including ocular coloboma, heart defects, choanal atresia, retarded growth and development, genitourinary hypoplasia and ear abnormalities 1 . Despite 70–90% of CHARGE syndrome cases resulting from mutations in the gene CHD7 , which encodes an ATP-dependent chromatin remodeller, the pathways underlying the diverse phenotypes remain poorly understood 2 . Surprisingly, our studies of a knock-in mutant mouse strain that expresses a stabilized and transcriptionally dead variant of the tumour-suppressor protein p53 (p53 25,26,53,54 ) 3 , along with a wild-type allele of p53 (also known as Trp53 ), revealed late-gestational embryonic lethality associated with a host of phenotypes that are characteristic of CHARGE syndrome, including coloboma, inner and outer ear malformations, heart outflow tract defects and craniofacial defects. We found that the p53 25,26,53,54 mutant protein stabilized and hyperactivated wild-type p53, which then inappropriately induced its target genes and triggered cell-cycle arrest or apoptosis during development. Importantly, these phenotypes were only observed with a wild-type p53 allele, as p53 25,26,53,54 /− embryos were fully viable. Furthermore, we found that CHD7 can bind to the p53 promoter, thereby negatively regulating p53 expression, and that CHD7 loss in mouse neural crest cells or samples from patients with CHARGE syndrome results in p53 activation. Strikingly, we found that p53 heterozygosity partially rescued the phenotypes in Chd7 -null mouse embryos, demonstrating that p53 contributes to the phenotypes that result from CHD7 loss. Thus, inappropriate p53 activation during development can promote CHARGE phenotypes, supporting the idea that p53 has a critical role in developmental syndromes and providing important insight into the mechanisms underlying CHARGE syndrome.

Background There are approximately 8,000 different rare diseases that affect roughly 400 million people worldwide. Many of them suffer from delayed diagnosis. Ciliopathies are rare monogenic disorders characterized by a significant phenotypic and genetic heterogeneity that raises an important challenge for clinical diagnosis. Diagnosis support systems (DSS) applied to electronic health record (EHR) data may help identify undiagnosed patients, which is of paramount importance to improve patients’ care. Our objective was to evaluate three online-accessible rare disease DSSs using phenotypes derived from EHRs for the diagnosis of ciliopathies. Methods Two datasets of ciliopathy cases, either proven or suspected, and two datasets of controls were used to evaluate the DSSs. Patient phenotypes were automatically extracted from their EHRs and converted to Human Phenotype Ontology terms. We tested the ability of the DSSs to diagnose cases in contrast to controls based on Orphanet ontology. Results A total of 79 cases and 38 controls were selected. Performances of the DSSs on ciliopathy real world data (best DSS with area under the ROC curve = 0.72) were not as good as published performances on the test set used in the DSS development phase. None of these systems obtained results which could be described as “expert-level”. Patients with multisystemic symptoms were generally easier to diagnose than patients with isolated symptoms. Diseases easily confused with ciliopathy generally affected multiple organs and had overlapping phenotypes. Four challenges need to be considered to improve the performances: to make the DSSs interoperable with EHR systems, to validate the performances in real-life settings, to deal with data quality, and to leverage methods and resources for rare and complex diseases. Conclusion Our study provides insights into the complexities of diagnosing highly heterogenous rare diseases and offers lessons derived from evaluation existing DSSs in real-world settings. These insights are not only beneficial for ciliopathy diagnosis but also hold relevance for the enhancement of DSS for various complex rare disorders, by guiding the development of more clinically relevant rare disease DSSs, that could support early diagnosis and finally make more patients eligible for treatment.

Congenital central hypoventilation syndrome (CCHS or Ondine's curse; OMIM 209880) is a life-threatening disorder involving an impaired ventilatory response to hypercarbia and hypoxemia. This core phenotype is associated with lower-penetrance anomalies of the autonomic nervous system (ANS) including Hirschsprung disease and tumors of neural-crest derivatives such as ganglioneuromas and neuroblastomas. In mice, the development of ANS reflex circuits is dependent on the paired-like homeobox gene Phox2b . Thus, we regarded its human ortholog, PHOX2B , as a candidate gene in CCHS. We found heterozygous de novo mutations in PHOX2B in 18 of 29 individuals with CCHS. Most mutations consisted of 5–9 alanine expansions within a 20-residue polyalanine tract probably resulting from non-homologous recombination. We show that PHOX2B is expressed in both the central and the peripheral ANS during human embryonic development. Our data support an essential role of PHOX2B in the normal patterning of the autonomous ventilation system and, more generally, of the ANS in humans.

Congenital hydrocephalus is a common condition caused by the accumulation of cerebrospinal fluid in the ventricular system. Four major genes are currently known to be causally involved in hydrocephalus, either isolated or as a common clinical feature: L1CAM , AP1S2 , MPDZ and CCDC88C. Here, we report 3 cases from 2 families with congenital hydrocephalus due to bi-allelic variations in CRB2, a gene previously reported to cause nephrotic syndrome, variably associated with hydrocephalus. While 2 cases presented with renal cysts, one case presented with isolated hydrocephalus. Neurohistopathological analysis allowed us to demonstrate that, contrary to what was previously proposed, the pathological mechanisms underlying hydrocephalus secondary to CRB2 variations are not due to stenosis but to atresia of both Sylvius Aqueduct and central medullar canal. While CRB2 has been largely shown crucial for apico-basal polarity, immunolabelling experiments in our fetal cases showed normal localization and level of PAR complex components (PKCι and PKCζ) as well as of tight (ZO-1) and adherens (β-catenin and N-Cadherin) junction molecules indicating a priori normal apicobasal polarity and cell–cell adhesion of the ventricular epithelium suggesting another pathological mechanism. Interestingly, atresia but not stenosis of Sylvius aqueduct was also described in cases with variations in MPDZ and CCDC88C encoding proteins previously linked functionally to the Crumbs (CRB) polarity complex, and all 3 being more recently involved in apical constriction, a process crucial for the formation of the central medullar canal. Overall, our findings argue for a common mechanism of CRB2 , MPDZ and CCDC88C variations that might lead to abnormal apical constriction of the ventricular cells of the neural tube that will form the ependymal cells lining the definitive central canal of the medulla. Our study thus highlights that hydrocephalus related to CRB2 , MPDZ and CCDC88C constitutes a separate pathogenic group of congenital non-communicating hydrocephalus with atresia of both Sylvius aqueduct and central canal of the medulla.

Background CDG2L (MIM#614576) is an autosomal recessive multisystemic disorder due to variants in COG6 gene. Postnatal phenotypes are now well described, while prenatal presentations remain poorly investigated. Only 8 of the 28 published patients have had prenatal ultrasound anomalies reported and no one post‐mortem investigation. Methods We used whole‐exome sequencing in a consanguineous Turkish family with four siblings presenting with Pierre Robin sequence, arthrogryposis, heart malformation, splenomegaly, hydrocephaly, corpus callosum dysgenesis, brainstem, and cerebellar hypoplasia. Results We identified a novel homozygous pathogenic variant in exon 9 of COG6 (NM_020751.2): c.821del, p.(Arg274Lysfs*32). In this family, our post‐mortem study led us to describe further the prenatal phenotype of CDG2L. In addition, it permits correlating the most relevant anomalies to a maldevelopmental cascade due to a neurodegenerative process of metabolic origin, affecting the entire central nervous system including the spinal cord. Conclusion In this context of recurrence of multisystemic disease diagnosed antenatally, exome sequencing is powerful to give a precise diagnosis and allows proposing a molecular prenatal diagnosis at the following pregnancy.

Background: Oesophageal atresia (OA) and mandibulofacial dysostosis (MFD) are two congenital malformations for which the molecular bases of syndromic forms are being identified at a rapid rate. In particular, the EFTUD2 gene encoding a protein of the spliceosome complex has been found mutated in patients with MFD and microcephaly (MIM610536). Until now, no syndrome featuring both MFD and OA has been clearly delineated. Results: We report on 10 cases presenting with MFD, eight of whom had OA, either due to de novo 17q21.31 deletions encompassing EFTUD2 and neighbouring genes or de novo heterozygous EFTUD2 loss-of-function mutations. No EFTUD2 deletions or mutations were found in a series of patients with isolated OA or isolated oculoauriculovertebral spectrum (OAVS). Conclusions: These data exclude a contiguous gene syndrome for the association of MFD and OA, broaden the spectrum of clinical features ascribed to EFTUD2 haploinsufficiency, define a novel syndromic OA entity, and emphasise the necessity of mRNA maturation through the spliceosome complex for global growth and within specific regions of the embryo during development. Importantly, the majority of patients reported here with EFTUD2 lesions were previously diagnosed with Feingold or CHARGE syndromes or presented with OAVS plus OA, highlighting the variability of expression and the wide range of differential diagnoses.

Objective Biallelic titin truncating variants (TTNtv) have been associated with a wide phenotypic spectrum, ranging from complex prenatal muscle diseases with dysmorphic features to adult‐onset limb‐girdle muscular dystrophy, with or without cardiac involvement. Given the size and complexity of TTN, reaching an unequivocal molecular diagnosis and precise disease prognosis remains challenging. Methods In this case series, 12 unpublished cases and one already published case with biallelic TTNtv were collected from multiple international medical centers between November 2022 and September 2023. TTN mutations were detected through exome or genome sequencing. Information about familial and personal clinical history was collected in a standardized form. RNA‐sequencing and analysis of TTN exon usage were performed on an internal sample cohort including postnatal skeletal muscles, fetal skeletal muscles, postnatal heart muscles, and fetal heart muscles. In addition, publicly available RNA‐sequencing data was retrieved from ENCODE. Results We generated new RNA‐seq data on TTN exons and identified genotype–phenotype correlations with prognostic implications for each titinopathy patient (whether worsening or improving in prenatal and postnatal life) using percentage spliced in (PSI) data for the involved exons. Interestingly, thanks to exon usage, we were also able to rule out a titinopathy diagnosis in one prenatal case. Interpretation This study demonstrates that exon usage provides valuable insights for a more exhaustive clinical interpretation of TTNtv; additionally, it may serve as a model for implementing personalized medicine in many other genetic diseases, since most genes undergo alternative splicing.

CREBBP truncating mutations and deletions are responsible for the well-known Rubinstein-Taybi syndrome. Recently, a new, distinct CREBBP-linked syndrome has been described: missense mutations located at the 3' end of exon 30 and the 5' portion of exon 31 induce Menke-Hennekam syndrome. Patients with this syndrome present a recognizable facial dysmorphism, intellectual disability of variable severity, microcephaly, short stature, autism, epilepsy, visual and hearing impairments, feeding problems, upper airway infections, scoliosis, and/or kyphosis. To date, all diagnoses were made postnatally. Trio-whole exome sequencing (WES) was performed in a fetus showing increased nuchal translucency persistence and aorta abnormalities at 28 weeks of gestation (WG). WES revealed a CREBBP de novo missense mutation (c.5602C>T; p.Arg1868Trp) in exon 31, previously reported as the cause of Menke-Hennekam syndrome. Termination of pregnancy was performed at 32 WG. We further reviewed the prenatal signs of Menke-Hennekam syndrome already reported. Among the 35 patients reported and diagnosed postnatally up to this day, 15 presented recognizable prenatal signs, the most frequent being intra-uterine growth retardation, brain, and cardiovascular anomalies. Menke-Hennekam is a rare syndrome with unspecific, heterogeneous, and inconstant prenatal symptoms occurring most frequently with the c.5602C>T, p.(Arg1868Trp) mutation. Therefore, the prenatal diagnosis of Menke-Hennekam syndrome is only possible by molecular investigation. Moreover, this case report and review reinforce the importance of performing prenatal WES when unspecific signs are present on imaging.

Ciliopathies are rare genetic diseases marked by considerable phenotypic heterogeneity and overlap. Among the key mechanisms of cilium biology, its compartmentalization is achieved through gating complexes and active transport such as intraflagellar transport (IFT). Among the IFT components, IFT27 plays a role in BBSome-mediated transport of ciliary membrane proteins required for ciliary signaling. While this gene was first linked to Bardet-Biedl syndrome, we next expanded its phenotypic spectrum to a fetal lethal ciliopathy. Here, we identified a second fetal case with short ribs, polydactyly, hypodysplastic kidneys, imperforate anus, and situs inversus . Genome sequencing identified novel biallelic variants in IFT27 . Functional analysis of tissues from both fetal cases revealed that all the identified variants lead to mRNA decay. Immunohistochemistry on fetal kidney sections showed that those variants are associated with altered ciliogenesis. Overall, we showed that complete loss of IFT27 function leads to a severe phenotypic spectrum overlapping with short ribs polydactyly and Pallister-Hall syndromes. In addition, our results argue for a role of IFT27 in ciliogenesis in humans.

Severe ventriculomegaly is a rare congenital brain defect, usually detected in utero, of poor neurodevelopmental prognosis. This ventricular enlargement can be the consequence of different mechanisms: either by a disruption of the cerebrospinal fluid circulation or abnormalities of its production/absorption. The aqueduct stenosis is one of the most frequent causes of obstructive ventriculomegaly, however, fewer than 10 genes have been linked to this condition and molecular bases remain often unknown. We report here 4 fetuses from 2 unrelated families presenting with ventriculomegaly at prenatal ultra-sonography as well as an aqueduct stenosis and skeletal abnormalities as revealed by fetal autopsy. Genome sequencing identified biallelic pathogenic variations in LIG4, a DNA-repair gene responsible for the LIG4 syndrome which associates a wide range of clinical manifestations including developmental delay, microcephaly, short stature, radiation hypersensitivity and immunodeficiency. Thus, not only this report expands the phenotype spectrum of LIG4-related disorders, adding ventriculomegaly due to aqueduct stenosis, but we also provide the first neuropathological description of fetuses carrying LIG4 pathogenic biallelic variations.